The Speaker Michael Martin has blocked an official Commons inquiry into his handling of the Damian Green affair, sparking fresh unrest about his position.

The inquiry cannot go ahead without Mr Martin's signature

By Melissa Kite, Deputy Political Editor

2:28PM GMT 20 Dec 2008

Up to 20 MPs are understood to have written to Mr Martin requesting that he authorise an investigation by The Standards and Privileges Committee into the controversial police search of Mr Green's Commons office last month.

But Mr Martin refused to sign off the inquiry, which means that it cannot go ahead. Tory MPs who wrote to the Speaker demanding the move are furious at his refusal and say it will only intensify demands for him to resign. One senior Tory said: "When the House comes back after Christmas pressure will be put on the Speaker to take action. Everybody agrees that the thing has been badly handled. We are not looking for scapegoats but to make sure this can't happen again."

Even Labour MPs, who have overwhelmingly supported Mr Martin throughout the Green debacle, expressed surprise at his decision to block a Standards and Privileges inquiry. One minister said: "I suppose the process is entirely up to the Speaker and the Speaker has said no and he doesn't have to provide any reasons why he said no." Another MP said: "It could have lanced the boil. As it is, those who oppose him are even more angry and suspicious now." The investigation into Mr Green is likely to conclude soon and prosecutors are almost certain to block charges. A report into the police handling of the affair has suggested that Metropolitan Police officers breached guidelines and good practice, and may have been heavy handed in their approach.

The Tories, meanwhile, say they would like to see Mr Martin make a statement announcing his intention to retire at the next election, at which point they would allow him to bow out gracefully.